/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */
package org.apache.iotdb.db.query.reader.chunk;

import org.apache.iotdb.db.engine.querycontext.ReadOnlyMemChunk;
import org.apache.iotdb.tsfile.read.TimeValuePair;
import org.apache.iotdb.tsfile.read.common.BatchData;
import org.apache.iotdb.tsfile.read.filter.basic.Filter;
import org.apache.iotdb.tsfile.read.reader.IChunkReader;
import org.apache.iotdb.tsfile.read.reader.IPageReader;
import org.apache.iotdb.tsfile.read.reader.IPointReader;

import java.io.IOException;
import java.util.Collections;
import java.util.List;

/**
 * To read chunk data in memory
 */
public class MemChunkReader implements IChunkReader, IPointReader {

    private IPointReader timeValuePairIterator;
    private Filter filter;
    private boolean hasCachedTimeValuePair;
    private TimeValuePair cachedTimeValuePair;
    private List<IPageReader> pageReaderList;

    public MemChunkReader(ReadOnlyMemChunk readableChunk, Filter filter) {
        timeValuePairIterator = readableChunk.getPointReader();
        this.filter = filter;
        // we treat one ReadOnlyMemChunk as one Page
        this.pageReaderList =
                Collections.singletonList(
                        new MemPageReader(
                                readableChunk.getTsBlock(), readableChunk.getChunkMetaData(), filter));
    }

    @Override
    public boolean hasNextTimeValuePair() throws IOException {
        if (hasCachedTimeValuePair) {
            return true;
        }
        while (timeValuePairIterator.hasNextTimeValuePair()) {
            TimeValuePair timeValuePair = timeValuePairIterator.nextTimeValuePair();
            if (filter == null
                    || filter.satisfy(timeValuePair.getTimestamp(), timeValuePair.getValue().getValue())) {
                hasCachedTimeValuePair = true;
                cachedTimeValuePair = timeValuePair;
                break;
            }
        }
        return hasCachedTimeValuePair;
    }

    @Override
    public TimeValuePair nextTimeValuePair() throws IOException {
        if (hasCachedTimeValuePair) {
            hasCachedTimeValuePair = false;
            return cachedTimeValuePair;
        } else {
            return timeValuePairIterator.nextTimeValuePair();
        }
    }

    @Override
    public TimeValuePair currentTimeValuePair() throws IOException {
        if (!hasCachedTimeValuePair) {
            cachedTimeValuePair = timeValuePairIterator.nextTimeValuePair();
            hasCachedTimeValuePair = true;
        }
        return cachedTimeValuePair;
    }

    @Override
    public boolean hasNextSatisfiedPage() throws IOException {
        return hasNextTimeValuePair();
    }

    @Override
    public BatchData nextPageData() throws IOException {
        return pageReaderList.remove(0).getAllSatisfiedPageData();
    }

    @Override
    public void close() {
        // Do nothing because mem chunk reader will not open files
    }

    @Override
    public List<IPageReader> loadPageReaderList() {
        return this.pageReaderList;
    }
}
